The use of threshold extension is becoming more widespread. A need for a "new and improved" demodulator affording full threshold extension and greatly improved reliability has become evident. Over the years it has been common to use phase detectors and phase locked loops in threshold extension applications. Certain barriers prevented optimum threshold extension. However, using a novel approach to solving these barriers lead to a new and unique way of demodulating FM in a deviation compression feedback FM demodulator, and now the use of narrower band pass filters in the IF stages and higher feedback loop gains is possible, permitting the fullest threshold extension possible. The effects of narrower band pass filters and higher feedback loop gain can be better understood in two publications entitled "Phase Locked Loops & Their Applications" by D. D. Carpenter, IEEE Press 1979, pages 178-181, and "Feedback and Control Systems" by A. C. McDonald/H. Lowe, Reston Publishing Co., Inc. 1981, pages 286-297 and 377-381 each of these providing insight to the effects of narrow band pass IF stages and high feedback loop gains. While other threshold extension demodulators provide a degree of improvement over conventional FM demodulators and especially conventional quadrature demodulators, there was still a need for a full threshold demodulator, and especially one providing a high degree of reliability.